Render Cache not using GPU

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gabe67

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Render Cache not using GPU

PostThu Oct 21, 2021 5:19 pm

Hi, I have some h264 footage in the timeline and set ProRes HQ as render codec. When I turn on render color output, everything is rendered via the CPU while GPU shows no usage whatsoever. Playback does seem to utilize the GPU by approx 10% but that’s it. Seems like a waste to me. Anybody know how to troubleshoot this? The GPU does show up in the preferences.
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Uli Plank

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Re: Render Cache not using GPU

PostThu Oct 21, 2021 6:01 pm

The use of the GPU for decoding H.264 may not be shown in usage statistics.
And then, ProRes will only be done by GPU in the newest Apple laptops.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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gabe67

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Re: Render Cache not using GPU

PostThu Oct 21, 2021 7:34 pm

Thank you for clarifying. Is there another codec that would work better for caching?
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Uli Plank

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Re: Render Cache not using GPU

PostThu Oct 21, 2021 7:40 pm

Since you are on a Mac, not really.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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gabe67

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Re: Render Cache not using GPU

PostThu Oct 21, 2021 8:08 pm

What would you use on a PC? Dnxhd?
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TheBloke

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Re: Render Cache not using GPU

PostThu Oct 21, 2021 8:31 pm

DNxHR, not DNXHD. HD is an old and outdated codec which can't do all resolutions.
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gabe67

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Re: Render Cache not using GPU

PostFri Oct 22, 2021 12:06 am

Is the DNX GPU accelerated only on PC or Mac also?
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TheBloke

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Re: Render Cache not using GPU

PostFri Oct 22, 2021 6:26 am

gabe67 wrote:Is the DNX GPU accelerated only on PC or Mac also?
DNxHR isn't GPU accelerated. Nor is ProRes.

ProRes is accelerated on M1 Macs - and a Mac Pro 2019 with a ProRes accelerator card - because Apple has made special hardware to do that, and Resolve supports that hardware. To my knowledge no-one has made DNxHR accelerator hardware - Avid would be the company that would be most likely to do that, and they don't seem to have done so.

However, the whole point of ProRes and DNxHR is that they're very quick and lightweight. Encoding/decoding ProRes and DNxHR will be much faster and more fluid than H264/H265. That's why those codecs are recommended for proxies, and provide a much nicer editing experience. It uses some CPU to encode/decode them, but not much, and they decode much faster than GPU accelerated H264/H265.
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Re: Render Cache not using GPU

PostFri Oct 22, 2021 7:07 am

Ok, so these two codecs are still the best bet then. It sounded like there was a better option on Windows, but I don't see what it might be.
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Re: Render Cache not using GPU

PostFri Oct 22, 2021 7:47 am

You could try Cineform under Windows. It's a wavelet codec, which decodes easier at fractional resolutions.
But then, your bottleneck might not be either of these codecs, maybe your storage or decoding of H.264.
Both ProRes and DNxHR are pretty light for the machine.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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gabe67

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Re: Render Cache not using GPU

PostFri Oct 22, 2021 1:27 pm

Ok, then I will stick to that. Did anybody test the ne M1 for Prores performance yet?
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Uli Plank

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Re: Render Cache not using GPU

PostFri Oct 22, 2021 3:09 pm

If you are referring to the M1Pro, mine should be here in 10 to 12 days.
But ProRes is pretty snappy on my stopgap Mac mini M1 too.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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roger.magnusson

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Re: Render Cache not using GPU

PostFri Oct 22, 2021 3:41 pm

I've never heard anyone say they needed hardware acceleration for encoding/decoding ProRes (at "normal" resolutions). It's lightweight by design and is rarely a bottleneck for real-time performance.

It does make sense for laptops though, where offloading the CPU has a much bigger effect in terms of battery life and thermals.
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gabe67

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Re: Render Cache not using GPU

PostSat Oct 23, 2021 7:57 am

Well, yes. But let’s see what the M1 pro and Max will be able to do.. maybe we will realize that it’s far superior. After all the GPU is superior to CPU rendering in any case. I only have an 8 core CPU for example.
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Uli Plank

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Re: Render Cache not using GPU

PostSat Oct 23, 2021 12:45 pm

That should not be the bottleneck. For DR, the GPU matters much more and the new M1 models may be stronger than most current laptops, but any good desktop machine should be ahead.
And then, ProRes is not hard for your machine. There are many more demanding features in DR than de- or encoding ProRes.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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gabe67

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Re: Render Cache not using GPU

PostSat Oct 23, 2021 3:01 pm

My CPU is at 90% when caching the timeline in ProRes and I am assuming that it will cache much faster using GPU. So when you say encoding is not the bottleneck, what do you think is the bottleneck? Decoding takes like 8% of my GPU and the RAID is not even anywhere close to max speed performance.
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